Sulfolane compounds are useful in a variety of industrial applications such as, for example, in pesticidal compositions, intermediates in the production of other organic chemicals, selective solvents to separate aromatic compounds from petroleum fractions, and selective solvents in alkylation of olefins.
Sulfolane compounds are generally prepared by catalytic hydrogenation of the corresponding sulfolene compounds. The sulfolene compounds are prepared by the reaction of a conjugated diene such as, for example, 1,3-butadiene, and sulfur dioxide at elevated temperatures.
However, the sulfolene compounds thus-produced are generally unstable and tend to decompose at mildly elevated temperatures into an unsaturated organic compound and sulfur dioxide. Furthermore, when the sulfolene compounds are used to prepare the corresponding sulfolane compounds by catalytic hydrogenation, the initiation of hydrogenation reaction may also increase the temperature enough to result in some decomposition of the sulfolene. Some of these decomposed products polymerize and the resulting polymer coats the hydrogenation catalyst significantly reducing its activity. Moreover, unreacted sulfur dioxide and the sulfur dioxide obtained from decomposition of sulfolene compounds also interfere with the subsequent catalytic hydrogenation. These sulfur dioxides must be removed or substantially reduced.
Processes have been developed for inhibiting the formation of polymers and reduction of sulfur dioxide in the production of sulfolane compounds. For example, amines have been used as inhibitors in reducing the amount of polysulfone polymer formation. Oxidizing agents have been used to reduce sulfur dioxide and other impurities. However, there is an ever present need to develop still more effective methods of reducing the polymer formation, the removal of sulfur dioxide and impurities, and the hydrogenation process so that the amount of hydrogenation catalyst used can be reduced and the production of sulfolane compounds can be greatly improved.